The invention relates to a seal member for effecting a leak-proof joint between an underground conduit and a structure such as a manhole well.
Different methods have been used in the past for effecting a coupling seal between an underground pipe or conduit and a manhole well provided with an aperture through which the end of the conduit is passed for leading to the interior of the manhole well. Such couplings may be effected by means of a bell-shaped packing or seal closely fitting the peripheral surface of the conduit and partially embedded in concrete or cement poured around the seal at the junction between the conduit and the aperture in the manhole well, or by forcing a packing into the space between the peripheral surface of the conduit and the edge of the aperture. Couplings of this type are disclosed in U.S. Pat. Nos. 2,087,752, 2,657,079, 3,591,190, 3,744,806, 3,787,061, 3,879,067 and 3,348,850.
Another method for effecting a seal between a conduit and a manhole well consists in placing a flanged seal member through the manhole well opening and clamping the flange over the aperture or embedding it in concrete or cement, the sleeve or boot portion of the seal member projecting outwardly from the manhole well opening. The end of the conduit is passed through the sleeve and the sleeve is clamped against the peripheral surface of the conduit by means of a steel strap clamp. A coupling of this type is disclosed in U.S. Pat. No. 3,759,280.
Underground conduits, usually made of clay, concrete, asbestos, plastic, such as polyvinyl chloride, or sometimes cast iron, generally have a rough outer surface, and are subject to wide variations in roundness and in outer diameter size dimensions. Often, conduits of a desired size are not immediately available on the market, and a contractor may be forced to utilize underground conduits of a slightly different outside diameter than the one contemplated.
Furthermore, it often happens that through use and aging, and due to settling of the ground in which an underground sewer system is buried, that bending moments and sheer forces are applied at the joints between the conduits and the manhole well openings causing undesired leakage from the manhole well to the surrounding ground or from the surrounding ground into the manhole well.